ROLE OF INTESTINAL MUCUS IN TRANSEPITHELIAL PASSAGE OF BACTERIA ACROSS THE INTACT ILEUM IN-VITRO

Background. Although gastrointestinal mucus is one of a number of puta tive host defense mechanisms that protect the gut barrier against micr obial translocation, little experimental data are available to show it s role in this process. The present study sought to determine the role of mucus depletion on the transepithelial passage of bacteria across viable segments of rat ileum mounted in Ussing chambers in vitro. Meth ods. Intestinal mucus as depleted in 12 rats after injection with pilo carpine (160 mg/kg intraperitoneally) 45 minutes before intestinal har vest. The mucosal surfaces of the perfused gut segments mounted in the Ussing chamber were exposed to 5 X 10(9) CFU/ml Escherichia coli C-25 . Viability was monitored ny continuous measurements of the potential difference generated by the membranes. The electrical characteristics were unaltered by pilocarpine pretreatment or exposure to bacteria. Re sults. Bacterial passage occurred in 100% of pilocarpine membranes as compared with 33.3% in controls (p < 0.05). Pilocarpine-treated membra nes resulted in 19.9 +/- 7.5 mg of retrievable mucus as compared with 28.8 +/- 7.2 mg in controls (p < 0.05). Light and transmission electro n microscopy revealed an intact epithelial surface in all membranes. T here was a marked decrease in mucus on the surface of pilocarpine-trea ted membranes. Conclusions. Intestinal mucus secretion is a critical f actor in the barrier function of the gut, and depletion results in a d ramatic increase in bacterial passage across the intact rat ileum.